1) Field of the Invention
This invention relates to a digital content rendering apparatus, a digital content rendering method for rendering a digital content based on the license information defining the specifics of permission of the rendering operation.
2) Description of the Related Art
In recent years, a multiplicity of DRMs (Digital Right Managements) providing a technique for protecting the copyright of a digital work have been developed. Especially, the commercial digital contents for movies and music, as represented by DVD, have been developed with the copyright strongly protected in a form advantageous to the contents provider.
The function of these techniques to protect the copyright is provided as a very rigid and stubborn mechanism in the presence of a strong desire to prevent the duplication of digital contents, and limits the freedom of the user more than analog contents.
The copyright law lays downs a provision of what is called the fair use whereby a work can be used without permission of the copyright holder by duplication or citation for private use. As to digital works, however, the freedom of the user is limited to prevent the duplication as described above, and therefore the duplication or citation for private use is prohibited. In view of this, the desire has increased for the fair use of digital works.
On the other hand, the copyright protection of non-commercial contents such as business documents, product catalogs, personal home pages, electronic mails, or the like with the contents thereof routinely reused and secondarily processed currently draws less attention, and therefore these contents have yet to be safely distributed.
In this situation, the activities are being carded out for international standardization such as ISO/IEC 21000 (MPEG21) aimed at the distribution and management of various forms of digital contents. With regard to MPEG21, a digital item declaration language (DIDL) for expressing the composite content configured of a combination and connection of a plurality of contents has been standardized, whereby the composite content including a plurality of contents as component elements has become possible to handle. Further, a right expression language (REL) making possible flexible license description has also been standardized, and a supporting method for describing the license using REL has been proposed by USP Application Pub. No. US2003/0125976.
A technique for synthesizing a CM image and a video content and rendering a composite content using the information such as the age, sex, distribution history and purchase history of the user of the content has been proposed in Japanese Patent Application Laid-Open No. 2002-203119.
When the distribution and reuse of a composite content is intended, however, the assumption is required that the elements constituting the particular composite content are distributed and reused as individual contents or synthesized with other different contents for rendering. In such a case, the context information including the position as viewed from the whole or the relationship with other component elements is liable to be lost by the individual use of the component elements. As a result, the original intention of the author may be expressed erroneously or transmitted as insignificant information.
It may be considered that this inconvenience can be avoided by integrating the component elements indivisibly. Each component element, however, may be a complete work itself and not necessarily require other component elements. From the viewpoint of distribution of digital contents that can be readily reused, the process of integrating the component elements indivisibly leads to an increased cost of editing and right handling and rather constitutes a stumbling block to the sound redistribution of contents.
MPEG21/DIDL has a mechanism for expressing the structural information of the composite content while at the same time selecting the component elements to be rendered and excluding the other component elements at the time of rendering. When the composite content is distributed by division, the original structure cannot be restored. According to the technique of USP Application Pub. No. US2003/0125976 using MPEG21/REL, the use license can be set for each component element of the composite content, but the license description including the correlation between the contents is impossible.
In the technique described in Patent Application Laid-Open No. 2002-203119, the contents are individually synthesized based on the user information. This is not a mechanism for protecting the intention of the author, and once it is decomposed again and the component elements are distributed, the original structure cannot be restored.